Prevention and detection of plagiarism has formed the basis of much research, but student perceptions on plagiarism are arguably not well understood. This is particularly the case in the computing disciplines. This paper considers two aspects of the student experience: (i) the types of plagiaristic activity that students engage in, and (ii) the specific understanding of what plagiarism means for students who write computer programmes. In a recent study, data were collected from published material (books, published papers, websites), and online formative quizzes and questionnaires used by universities to test student knowledge of what constitutes plagiarism. Facet analysis was used to classify the data into four initial categories (sources, actions, material, extrinsic). Further analysis suggested a refinement to six categories and 23 sub-categories which directly relate to the computing disciplines. In a further study a large-scale online questionnaire was carried out to obtain the perceptions of students on source-code plagiarism. Data were collected from 770 students studying at 21 higher education institutions in the UK and overseas. This study's results suggest that certain types of plagiaristic activity are poorly understood. This paper summarises and compares the results of these two studies and reflects on the implications for educating computing students about how they should avoid plagiarism